Lenovo Legion 5 has a newer NVIDIA Optimus technology that introduces MUX switch. This means that when you turn MUX switch, it turns off the secondary GPU and runs strictly on NVIDIA RTX GPU. On some laptops MUX switch is called Hybrid Mode but it's the same thing.
What you are saying is correct, but only for older NVIDIA Optimus technology, where there was no MUX switch. On old NVIDIA Optimus turning off integrated GPU would cause both graphics cards to function incorrectly, basically forcing the entire OS to use Microsoft Basic Driver just like you mentioned. My old laptop had NVIDIA Optimus 2 technology and it did exactly that. But in that case everything would just work badly.
But with MUX switch all applications are forced to use NVIDIA RTX GPU just like as if it was a laptop with only one GPU. When MUX is on, applications can only see NVIDIA GeForce RTX 3060 Laptop GPU.
Tomb Raider III, IV and V have stable 30 FPS (TR is by design capped to 30fps) on 1920x1080. TR3 is buttery smooth, but TR4 and 5 feel choppy.
Black Mirror has 25FPS
Gothic 2 runs with 500FPS in Xardas Tower and 125FPS outside of the tower. Biggest hits are in the port town but still over 60 FPS in 1920x1080
Dracula 3 has weird tendency on working great at first then suddenly taking a real hit in performance eg. a week into gameplay, but I think this is caused by dgvoodoo 2 actually. The game doesn't work without it.
Harry Potter 1 has definitely bad performance, but from what I have noticed it depends on the OS. I tried on my laptop, my older W10 laptop and my mom's oldest Windows 8 laptop and they all have performance issue which is solved when you switch to DX9 renderer.
Honestly the more I play with the games the more I think this might be more game specific than I originally thought. Gothic 2 seems buttery smooth. Tomb Raider III is as smooth as a game can be with 30 FPS, but Tomb Raider IV and V is choppy even though framerate is consistent! Weird, considering TR 3, 4 and 5 run on similar engine that uses DX 6/6.1. Black Mirror is just sluggish but could be by design..?